This invention is in the field of biology and more particularly relates to the field of cell biology.
2. Description of the Prior Art
Epithelial cells are cells covering or lining body surfaces. Examples include epidermal cells of the skin and cells lining the mouth, nose, pharynx, esophagus and vagina. Many epithelial cells, though not all, are often referred to as keratinocytes because of their ability to synthesize keratin.
Although techniques for cultivation of many types of mammalian cells have long been known, most efforts to serially cultivate normal epithelial cells, including mammalian epidermal cells, have failed. Some of the numerous literature descriptions of attempts to serially cultivate disaggregated epidermal cells in monolayers are included in: F. L. Vaughan and I. A. Bernstein, J. Invest. Derm., 56, 454 (1971); M. A. Karasek and M. E. Charlton, J. Invest. Derm., 56, 205 (1971); N. E. Fusenig and P. K. M. Worst, J. Invest. Derm., 63, 187 (1974); and S. H. Yuspa, D. L. Morgan, R. J. Walker and R. R. Bates, J. Invest. Derm., 55, 379 (1970).
More recently, a technique was discovered for the serial cultivation of epidermal cells (keratinocytes) under very specific and controlled conditions. In this technique, human epidermal cells were grown in cultures together with fibroblast cells treated to prevent their multiplication. Fibroblast cell density was carefully controlled to allow epidermal cell colony formation and growth. It was also disclosed that some keratinocytes could be grown when fibroblast cell products were substituted for the fibroblast cells themselves. These techniques for serially cultivating epidermal cells and other epithelial cell types are described in U.S. Pat. No. 4,016,036 issued to Howard Green and James G. Rheinwald.